Linux and Uuix Security Manual

Author: Nitesh Dhanjani
Publisher:
Publish Date: 2004-07-01
Features: This book will tell you how hackers think so that you can find ways to protect Unix and Linux systems from their attacks. This is the only way to know how to prevent systems from being compromised. To stop experienced hackers, we need to understand their thought processes, techniques, and strategies. The powerful nature of Unix and Linux operating systems is a double-edged sword. In most cases, the source code of the operating system kernel is freely available, and administrators can make significant changes to the kernel to meet their needs. However, the powerful and flexible nature of Unix and Linux contains a lot of complexity, increasing the likelihood of dangerous misconfigurations. We also need to consider the differences among the various available Unix and Linux release versions. Each version is tied to its own set of security policies and configurations. For example, some release versions disable a set of remote services, while others enable all possible services with weak security policies. Hackers are aware of the complexity of managing Unix and Linux hosts and exactly know how to exploit them. The clever hacker strategies introduced in this book will surprise you, and the book will also teach you how to defend against these hacker attacks. Don’t worry that hackers will master the information provided in this book, because they already know it. The purpose of this book is to expose the attack strategies currently used by hackers so that you can learn how to counter them. Once you understand how hackers think and the various methods they use to infiltrate systems, the situation will be in your favor. This book will tell you how hackers think so that you can find ways to protect Unix and Linux systems from their attacks. This is the only way to know how to prevent systems from being compromised. To stop experienced hackers, we need to understand their thought processes, techniques, and strategies. The powerful nature of Unix and Linux operating systems is a double-edged sword. In most cases, the source code of the operating system kernel is freely available, and administrators can make significant changes to the kernel to meet their needs. However, the powerful and flexible nature of Unix and Linux contains a lot of complexity, increasing the likelihood of dangerous misconfigurations. We also need to consider the differences among the various available Unix and Linux release versions. Each version is tied to its own set of security policies and configurations. For example, some release versions disable a set of remote services, while others enable all possible services with weak security policies. Hackers are aware of the complexity of managing Unix and Linux hosts and exactly know how to exploit them. The clever hacker strategies introduced in this book will surprise you, and the book will also teach you how to defend against these hacker attacks. Don’t worry that hackers will master the information provided in this book, because they already know it. The purpose of this book is to expose the attack strategies currently used by hackers so that you can learn how to counter them. Once you understand how hackers think and the various methods they use to infiltrate systems, the situation will be in your favor.
Organization of the Book This book is divided into four main parts: Part I: Hacker Intrusion Techniques and Defenses This part of the book discusses the intrusion techniques currently widely used by hackers and introduces defense techniques against all the intrusion techniques described in these chapters. In Chapter 1, we start by understanding the logical steps of intrusion techniques: tracking. This chapter will tell you how hackers obtain public information through search engines, registration records, DNS records, and more. Once they have gathered all available information from public resources, they begin the actual identification and scanning of networks and hosts. In Chapter 2, this chapter tells you how to determine which hosts are running in a network and which ports they are open. We will discuss different methods of port scanning, as well as operating system identification techniques and tools. In Chapter 3, learn how hackers identify applications and services running on remote hosts. This chapter will introduce various tools and methods used by potential intruders to enumerate usernames and remote services. In Chapter 4, this chapter discloses the specific tools and strategies hackers use to gain access to vulnerable hosts. Learn the clever techniques used by hackers, such as brute force cracking, sniffing, man-in-the-middle attacks, password cracking, port redirection, and exploiting misconfigured, buffer overflows, and other software system security vulnerabilities. In Chapter 5, exploiting specific vulnerabilities often allows hackers to gain privileges of a non-privileged user or system account. In these cases, the next step for hackers is to obtain superuser (root) privileges. This chapter shows the various methods hackers use to try to gain higher-level privileges. In Chapter 6, once a host is compromised, hackers want to hide their presence and ensure continuous and privileged access to the host. This chapter will tell you how hackers hide their tracks by clearing important logs and how hackers install trojan horses, backdoors, and rootkit attack tools on compromised target hosts.
Part II: Host Security Hardening This second part of the book focuses on the multiple steps system administrators can take to harden default system configurations and policies. In Chapter 7, this chapter discusses important configuration issues related to hardening default application and server configurations. We encourage all system administrators to consider the suggestions in this chapter to prevent intruders from attacking weak system policies and configurations. In Chapter 8, malicious users and hackers often exploit improper user and file system permissions. This chapter will introduce UNIX and LINUX file permissions and describe the exact steps to defend against intrusions caused by poor user and file permissions. In Chapter 9, every system administrator should perform proper system event logging. This chapter will teach you how to enable and configure useful logging services and how to properly set permissions on log files to prevent them from being tampered with. It is also important to download new security patches in a timely manner. This chapter provides useful links to official websites where you can obtain this information.
Part III: Special Topics This third part of the book covers several exciting topics, including writing plug-ins for the Nessus scanner, wireless intrusion, and intrusion using a Zaurus PDA. In Chapter 10, Nessus is a currently popular vulnerability scanning tool. It is free and designed to be modular. This chapter will teach you how to use NASL (Nessus Attack Script Language) to write custom security vulnerability check plug-ins for the Nessus scanner. In Chapter 11, learn how hackers infiltrate 802.11 wireless networks. This chapter discusses the weaknesses of the WEP protocol and introduces the tools used by hackers to infiltrate wireless networks. Additionally, this chapter offers some suggestions on how to better protect wireless networks. In Chapter 12, the Sharp Zaurus PDA device runs an embedded Linux operating system. This chapter will show you the various security tools used for the Zaurus PDA and how they are easily exploited by hackers to infiltrate wireless networks.
Reference Center This part is arranged at the end of the book for easy reference. When you need quick information about common commands, common ports, online resources, IP addresses, and useful Netcat commands, remember to turn to this part. Additionally, this part also provides ASCII values and HTTP response tables.
Words for Readers The author has made a lot of effort in writing this book. It is hoped that readers can find valuable information in the book. Most importantly, it is hoped that readers will use the information provided in this book to protect their own systems and networks from experienced hackers.